nber category 5 Mechanical subcat 53 Motors & Engines + Parts

uspto classes
91 Motors: Expansible Chamber Type
92 Expansible Chamber Devices
123 Internal-Combustion Engines
185 Motors: Spring, Weight, or Animal Powered
188 Brakes
192 Clutches and Power-Stop Control
251 Valves and Valve Actuation
303 Fluid-Pressure and Analogous Brake Systems
415 Rotary Kinetic Fluid Motors or Pumps
417 Pumps
418 Rotary Expansible Chamber Devices
464 Rotary Shafts, Gudgeons, Housings, and Flexible Couplings for Rotary Shafts
474 Endless Belt Power Transmission Systems or Components
475 Planetary Gear Transmission Systems or Components
476 Friction Gear Transmission Systems or Components
477 Interrelated Power Delivery Controls, Including Engine Control

Historic patent counts for subcat 53

uspto search in the 1790 to present database

ccl/91/$ OR ccl/92/$ OR ccl/123/$ OR ccl/185/$ OR ccl/188/$ OR ccl/192/$ OR ccl/251/$ OR ccl/303/$ OR ccl/415/$ OR ccl/417/$ OR ccl/418/$ OR ccl/464/$ OR ccl/474/$ OR ccl/475/$ OR ccl/476/$ OR ccl/477/$

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